Certain embodiments of the present invention relate to the detection of osteoporosis and more particularly relates to the detection of bone mineral density using a flat panel detector.
Osteoporosis is a disease of the skeleton in which the amount of calcium present in the bones slowly decreases to the point where the bones become brittle and prone to fracture. In other words, the bone loses density. Osteoporosis is diagnosed when bone density has decreased to the point where fractures occur even under mild stress, also referred to as the fracture threshold.
In the United States alone, ten million people have osteoporosis and eighteen million more have low bone mass (80% of whom are women), a condition which indicates an increased risk of developing osteoporosis. Osteoporosis is responsible for one-and-one-half million fractures annually. As a result, statistics indicate that one of every two women over age fifty will have an osteoporosis-related fracture in their lifetime. As a reference, a woman's risk of an osteoporosis-related fracture is equal to her combined risk of acquiring breast, uterine and ovarian cancer. The most common sites of fractures are the hip, spine, wrist and ribs. Perhaps the most devastating of these fractures is the hip fracture. On average, 24% of hip fractures in patients 50 and over lead to death within one year. Osteoporotic fractures such as these cost an estimated $18 billion annually.
Unfortunately, bone density loss occurs without symptoms. Bone mineral density (BMD) measurements can be used to detect osteoporosis before fracture, determine the probability of a future fracture, determine the rate of bone loss, and monitor the efficacy of treatment. Additionally, effective treatments currently exist, thus highlighting the desirability for early detection of the disease. Nonetheless, due to the lack of symptoms, osteoporosis is underdiagnosed and frequently goes undetected.
Due to the frequency of osteoporotic fractures, the National Osteoporosis Foundation (NOF) currently recommends broad categories of women to receive bone mineral density testing: all women ages 65 and older, postmenopausal women having any of the risk factors for osteoporotic fracture (low body weight, history of fracture, Asian or Caucasian, cigarette smoking, estrogen deficiency, early menopause, low calcium intake, alcoholism, recurrent falls, and inadequate physical activity), and all postmenopausal women who have already had a fracture. Additionally, many women with these same risk factors are recommended to have mammography tests. It may also be desirable to test women with these same risk factors for lung cancer, pneumonia, or a bone fracture.
There are two basic methods to measure the density of bone. These methods involve passing either X-rays or ultrasound waves through the bone being assessed, and measuring the effect that the bone has on these rays or waves. Within the field of X-rays, the measurement may utilize the principals of either radiogrammetry (i.e., standard X-ray techniques) or absorptiometry. In this context, radiogrammetry (or radiography) involves the use of registration on film of the differential absorption of X-ray beams passing through a specimen. Absorptiometry refers to a chemical analysis of gases, liquids or solids to measure densities, porosities as well as coating, plating and insulation thickness. In the context of osteoporosis, absorptiometry is use to measure bone densities. There are two types of absorptiometry, single energy X-ray absorptiometry (“SXA”) and dual energy X-ray absorptiometry (“DXA”). Single energy X-ray absorptiometry involves the use of X-rays at a single wavelength to measure bone mineral content (in the detection of osteoporosis). Dual energy X-ray absorptiometry involves the use of X-rays at two wavelengths to measure bone mineral content (in the detection of osteoporosis). DXA is used when SXA is not feasible, i.e., in areas with variable soft tissue and composition such as the spine or hip.
Two types of BMD tests used in diagnosing osteoporosis that utilize X-rays are peripheral BMD on the wrist or heel (radiogrammetry using a pencil beam or a fan beam), and dual energy X-ray absorptiometry on the hip, spine or femur. For example, osteoporosis tests and lung cancer tests are currently performed in separate units and/or stations (in separate rooms or areas): the osteoporosis test using a pencil beam or fan beam on the heel or wrist, and the lung cancer test using a standard radiography unit. While the scanning time for X-rays is generally short (on the order of less than one second), the setup time for each of these tests can take ten minutes or more.
Due to the overlap in symptoms, ages and gender in people who have osteoporosis and/or other disease states (e.g., breast cancer, lung cancer and pneumonia, chronic obstructive pulmonary disease, tuberculosis, bone fracture or an abnormally sized or shaped organ), there is a particular need for a dual-purpose screening method capable of detecting both osteoporosis (or BMD) and at least one other disease state.